(1) border ①: Germany is ready to launch a war of aggression; The Soviet Union protects itself; The Soviet Union and Germany signed a secret agreement to carve up Poland; Border ②: The Soviet Union and Germany invaded Poland respectively, and Poland perished; The Soviet Union split Poland.

(2) The victory of the anti-fascist war and the defeat of Germany; The victorious country decided to change the borders of Europe; Stabilize the Polish border; With the color of big country politics.